Crawfish are freshwater crustaceans. Louisiana has more than 30 different species of crawfish, but only two species are commercially important to the industry; the red swamp crawfish (Procambarus clarkii) and the white river crawfish (Procambarus zonangulus). Red crawfish far outnumber white crawfish in state-wide production. Occasionally both species are mixed in the same catch. Red crawfish dominate most farms, especially in south Louisiana and in most places in the Atchafalaya Basin. White crawfish are slightly more plentiful on north Louisiana farms and in Mississippi River overflow swamps.
Most crawfish are harvested between December and June, but March, April and May are the peak months in Louisiana. On rare occasions, crawfish may be harvested in July and August in the state.
When purchasing crawfish from a store, and not direct from the producer, read the label VERY carefully to see the country of origin; make sure it is not just distributed in the U.S.
Many thanks to LSUAgCenter for this great information on Louisiana crawfish.